Exhaust gas control apparatus and method

ABSTRACT

An exhaust gas control apparatus includes: a fuel supply portion that is provided so as to supply fuel to a portion of an exhaust passage, which is upstream of an exhaust gas purification member provided in the exhaust passage; a heating portion that is disposed between the fuel supply portion and the exhaust gas purification member; and a control portion that controls an amount of electric power that is supplied to the heating portion, based on an exhaust gas temperature and an exhaust gas flow rate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an exhaust gas control apparatus that purifies exhaust gas, an internal combustion engine including the same, and a method for controlling the same.

2. Description of Related Art

Japanese Patent Application Publication No. 2010-059886 (JP-A-2010-059886) describes an example of an exhaust gas control apparatus for an internal combustion engine. In the exhaust gas control apparatus, a compact oxidation catalyst, a fuel supply valve, and a glow plug are provided in an exhaust passage at positions upstream of an exhaust gas purification catalyst. The glow plug is disposed between the compact oxidation catalyst and the fuel supply valve. An injection orifice of the fuel supply valve faces an end face of the compact oxidation catalyst. The glow plug is disposed in such a position that the fuel injected from the fuel supply valve contacts a tip end of the glow plug. Respective operations of the fuel supply valve and the glow plug are controlled so that the fuel supply valve and the glow plug are operated in one of first to third control modes. In the first control mode, the fuel is supplied from the fuel supply valve and the glow plug heats the fuel, and consequently the fuel supplied from the fuel supply valve ignites. In the second control mode, the fuel is supplied from the fuel supply valve and the glow plug heats the fuel, but the fuel supplied from the fuel supply valve does not ignite. In the third control mode, the fuel is supplied from the fuel supply valve but the glow plug does not heat the fuel. The first or third control mode may be selected in an operation region in which ignition of the fuel is possible. The second or third control mode may be selected in an operation region in which ignition of the fuel is impossible.

In the exhaust gas control apparatus described in JP-A-2010-059886, the glow plug is provided in the exhaust passage. Therefore, exhaust gas may influence heating by the glow plug. For example, the degree to which the glow plug is cooled by the exhaust gas varies depending on the temperature of the exhaust gas. However, in order to appropriately control the temperature of the exhaust gas purification catalyst, it is desired that the fuel supplied to the exhaust passage be heated or combusted in the same manner regardless of variations in, for example, the temperature of the exhaust gas.

SUMMARY OF THE INVENTION

The invention provides an exhaust gas control apparatus that appropriately heats or combusts fuel supplied to an exhaust passage regardless of variations in the state of exhaust gas in the exhaust passage. The invention also provides an internal combustion engine including such exhaust gas control apparatus and a method for controlling such exhaust gas control apparatus.

A first aspect of the invention relates to an exhaust gas control apparatus. The exhaust gas control apparatus includes: an exhaust gas purification member that is Provided in an exhaust passage; a fuel supply portion that is provided so as to supply fuel to a portion of the exhaust passage, which is upstream of the exhaust gas purification member; a heating portion that is disposed between the fuel supply portion and the exhaust gas purification member; and a control portion that controls an amount of electric power that is supplied to the heating portion, based on an exhaust gas temperature and an exhaust gas flow rate.

The control portion may increase the amount of electric power that is supplied to the heating portion as the exhaust gas temperature decreases.

The control portion may increase the amount of electric power that is supplied to the heating portion as the exhaust gas flow rate increases.

The control portion may execute a control of correcting the amount of electric power that is supplied to the heating portion, based on an amount of fuel that is supplied from the fuel supply portion. The control portion may execute the control of correcting the amount of electric power that is supplied to the heating portion, such that the amount of electric power that is supplied to the heating portion increases as the amount of fuel that is supplied from the fuel supply portion increases.

A second aspect of the invention relates to an internal combustion engine configured to include the exhaust gas control apparatus described above.

A third aspect of the invention relates to a method for controlling an exhaust gas control apparatus. The exhaust gas control apparatus includes an exhaust gas purification member that is provided in an exhaust passage; a fuel supply portion that is provided so as to supply fuel to a portion of the exhaust passage, which is upstream of the exhaust gas purification member; and a heating portion that is disposed between the fuel supply portion and the exhaust gas purification member. The method includes: detecting an exhaust gas temperature; detecting an exhaust gas flow rate; and controlling an amount of electric power that is supplied to the heating portion, based on the exhaust gas temperature and the exhaust gas flow rate.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view showing an internal combustion engine to which an exhaust gas control apparatus according to a first embodiment of the invention is applied;

FIG. 2 is a flowchart for explaining operation control for a fuel supply valve and a glow plug according to the first embodiment; and

FIG. 3 is a flowchart for explaining operation control for the fuel supply valve and the glow plug according to a second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detail with reference to the attached drawings.

FIG. 1 is a schematic view of an internal combustion engine (hereinafter referred to as an engine) 10 to which an exhaust gas control apparatus 1 according to a first embodiment is applied. The engine 10 is a compression-ignition internal combustion engine, namely, a diesel engine, for an automobile. In FIG. 1, an exhaust system of the engine 10, which extends from an engine main body 10′, is partially shown in an exaggerated manner (an intake system, an engine internal mechanism, and the like are not shown).

In an exhaust passage 14 defined by an exhaust pipe 12 of the engine 10, a first catalyst converter 16 and a second catalyst converter 18 are provided in series in this order from an upstream side of the exhaust passage 14. A first exhaust gas purification member (hereinafter, also referred to as “first purification member”) 20 and a second exhaust gas purification member (hereinafter, also referred to as “second purification member”) 22 are accommodated in series in the first catalyst converter 16. A third exhaust gas purification member (hereinafter, also referred to as “third purification member”) 24 is accommodated in the second catalyst converter 18. Note that the first purification member 20, the second purification member 22, and the third purification member 24 are included in the exhaust gas control apparatus 1.

Here, the first purification member 20 includes an oxidation catalyst. The first purification member 20 is formed as a monolith catalyst that supports a precious metal catalyst such as platinum Pt.

The second purification member 22 is a particulate filter that traps particulate matter (PM) in the exhaust gas. The particulate filter serving as the second purification member 22 does not support a precious metal catalyst. However, the particulate filter may support, for example, a precious metal catalyst such as platinum Pt.

The third purification member 24 includes a NOx purification catalyst, which is a NOx storage-reduction catalyst here. The third purification member 24 includes a base, on which a catalyst support that is formed from alumina, for example, is supported. On the surface of the catalyst support, precious metal catalysts such as platinum Pt are supported at dispersed positions. Further, a layer of a NOx absorbent is also formed on the surface of the catalyst support. The NOx absorbent performs a NOx storage/release operation, that is, stores NOx when an air-fuel ratio of the exhaust gas is lean, and releases the stored NOx when an oxygen concentration in the exhaust gas decreases. The third purification member 24 with the above configuration stores NOx when the air-fuel ratio of the exhaust gas is lean, and releases the stored NOx to reduce the NOx when the oxygen concentration of in the exhaust gas decreases, e.g., the air-fuel ratio of the exhaust gas becomes rich. Note that the third purification member 24 may include a NOx purification catalyst that promotes a chemical reaction between ammonia and NOx (reduction reaction). In this case, for supplying ammonia, a urea aqueous solution supply device, for example, may be provided between the first catalyst converter 16 and the second catalyst converter 18.

The exhaust gas control apparatus 1 provided in the engine 10 further includes a temperature control device 30. The temperature control device 30 is provided so as to control temperatures of the exhaust gas purification members 20, 22, 24; more specifically, so as to heat the exhaust gas purification members 20, 22, 24. The temperature control device 30 is used to generate gas for heating the exhaust gas purification members 20, 22, 24 (hereinafter, referred to as “heating gas”) and supply the heating gas to the first to third purification members 20, 22, 24 downstream of the temperature control device 30, especially to the second purification member 22 and the third purification member 24, so as to maintain and promote warm-up or heating of the exhaust gas purification members and activated states thereof.

In particular, here, the temperature control device 30 operates such that the third purification member 24, which is one of the three exhaust gas purification members, is heated up to a temperature in a predetermined activation temperature range of the third purification member 24 and the temperature of the third purification member 24 is maintained within the predetermined activation temperature range. In addition, the temperature control device 30 operates at a predetermined timing and for a predetermined time period so that the particulate matter trapped by the second purification member 22 is removed. For example, each time a cumulative operation time of the engine 10 exceeds a predetermined value, the temperature control device 30 is operated. Note that the temperature control device 30 may operate when the pressure difference between an upstream side and a downstream side of the second purification member 22 becomes a predetermined value or more. In this case, it is desirable that a pressure sensor for detecting a pressure difference between the upstream side and the downstream side of the second purification member 22, that is, a pressure difference sensor, be provided.

The temperature control device 30 includes an oxidation promotion member 32, a fuel supply valve 34, and a glow plug 36 that are provided upstream of the exhaust gas purification members described above. The glow plug 36 is positioned downstream of the fuel supply valve 34. The oxidation promotion member 32 and the fuel supply valve 34 are arranged such that the fuel is injected from the fuel supply valve 34 toward the oxidation promotion member 32. The fuel supply valve 34 and the glow plug 36 are arranged such that the fuel is injected from the fuel supply valve 34 toward a tip end portion 36 a that is a heating section of the glow plug 36. That is, the fuel supply valve 34 is provided so as to supply fuel to a portion of the exhaust passage 14, which is upstream of the glow plug 36.

The oxidation promotion member 32 includes a catalyst having an oxidation function, more specifically, includes an oxidation catalyst. The oxidation promotion member 32 includes a catalyst member 32 a formed as a metal catalyst that supports a precious metal catalyst such as platinum Pt. The catalyst member 32 a of the oxidation catalyst 32 is fixed to and supported by the exhaust passage 14, via a support member (partially not shown) including a cylindrical member 32 b. Note that the oxidation promotion member 32 has a size and a shape that are determined such that the oxidation promotion member 32 does not to interfere with a flow of the exhaust gas in the exhaust passage 14. The oxidation promotion catalyst 32, especially the catalyst member 32 a, is smaller than the exhaust gas purification members such as the first purification member 20, and is sometimes referred to as a compact oxidation catalyst.

The fuel supply valve 34 is provided as a fuel supply portion. The fuel supply valve 34 may be provided such that an injection orifice thereof is positioned in the exhaust passage. However, the fuel supply valve 34 in the embodiment is provided in an extension passage for fuel supply (hereinafter referred to as a fuel passage) 37 that is provided so as to protrude from the exhaust passage 14. The fuel passage 37 is a passage for guiding the fuel supplied from the fuel supply valve 34 into the exhaust passage 14. Specifically, the fuel passage 37 is designed so as to guide the fuel supplied from the fuel supply valve 34 toward the tip end portion 36 a of the glow plug 36 and the catalyst member 32 a of the oxidation promotion member 32. The fuel supply valve 34 is provided so as to supply the exhaust passage with the fuel that is fed from a fuel tank 38, included in a fuel feed device which is equipped with a fuel injection valve for the engine main body 10′, and then pressurized by a pump 40. Thus, the fuel supply valve 34, the fuel tank 38, and the pump 40 here are included in a fuel supply device 42. The fuel supply device 42 also includes part of a control unit (described later), which functions as a control portion that controls operations of the fuel supply valve 34 and the pump 40. The pressure of the fuel that is injected from the fuel supply valve 34 is constant in this embodiment, although it may be variable. The pump 40 operates such that the pressure of the fuel that is infected from the fuel supply valve 34 is constant. Note that the fuel supply device 42 includes a mechanism that returns excess fuel to the fuel tank 38. However, the fuel supply valve 34 may be configured completely independent of the fuel feed device.

The glow plug 36 is provided as a heating portion. By energizing the glow plug 36, the tip end portion 36 a serving as the heating section of the glow plug 36 generates heat so that the fuel supplied from the fuel supply valve 34 and the exhaust gas are heated. The glow plug 36 serving as the heating portion is included in a heating device 44. The heating device 44 also includes part of the control unit (described later), which functions as a control portion that controls operation of the glow plug 36, namely, heat generation by the glow plug 36. The control portion included in the heating device 44 controls the operation of the glow plug 36, that is, energization of the glow plug 36. Specifically, the control portion included in the heating device 44 controls a glow plug control unit (hereinafter referred to as a GCU) 46 so as to control the amount of electric power supplied to the glow plug 36, thereby controlling the amount of heat generated by the tip end portion 36 a of the glow plug 36. The GCU 46 is provided so as to control a duty ratio in a duty control for the glow plug 36. By controlling the GCU 46, a voltage applied on the glow plug 36 is maintained constant but the duty ratio may be varied. Consequently, the amount of electric power supplied to the glow plug 36 may be varied. Note that the GCU 46 is connected to the glow plug 36 via a power supply 48. If a structure that makes the voltage applied on the glow plug 36 variable is provided, the voltage applied on the glow plug 36 may be varied, for example, so as to change the amount of electric power supplied to the glow plug 36. Note that, instead of the glow plug 36, a ceramic heater may be used as the heating portion.

The fuel injected from the fuel supply valve 34 passes a vicinity of the tip end portion 36 a of the glow plug 36, and reaches the oxidation promotion member 32 and its vicinity. When the tip end portion 36 a generates heat due to the energization of the glow plug 36, the fuel receives heat from the glow plug 36, combusts in some cases, and reaches the oxidation promotion member 32 and its vicinity. Then, the oxidation promotion member 32 promotes oxidation, e.g., combustion of the fuel. In particular, the oxidation promotion member 32 includes the oxidation catalyst here. Therefore, when the temperature of the oxidation promotion member 32 is within a predetermined activation temperature range, the oxidation promotion member 32 more suitably promotes oxidation of the fuel. Note that due to the oxidation of the fuel by the oxidation promotion member 32, the temperature of the oxidation promotion member 32 increases by itself. Thus, heating gas is generated and flows through the exhaust gas purification members 20, 22, 24. Such heating gas may have a high temperature due to the oxidation of the fuel.

In addition, the heating gas may contain a reformed fuel. When the temperature of the oxidation promotion member 32 increases, hydrocarbons having a large carbon number in unburned fuel decompose and hydrocarbons that have a small carbon number and that are highly reactive are generated in the oxidation promotion member 32, whereby the fuel is reformed into a highly reactive fuel. In other words, the oxidation promotion member 32 constitutes a quick heat generation device that quickly generates heat while constituting a reformed fuel discharger that discharges a reformed fuel. Note that there are cases where the fuel is not heated by the glow plug 36 when the fuel is supplied from the fuel supply valve 34 so as to generate the reformed fuel.

The operations of the fuel supply valve 34 and the glow plug 36 are controlled by a control unit 50. The control unit 50 has functions of the control portion that controls the operations of the fuel supply valve 34 and the glow plug 36 depending on the operation state of the engine, the temperatures of the exhaust gas purification members, or the like. Operation modes of the fuel supply valve 34 and the glow plug 36 are roughly classified into the following two modes. In a first operation mode, fuel is supplied from the fuel supply valve 34 and the fuel is heated by the glow plug 36 to promote combustion or reformation of the fuel. In a second operation mode, the fuel is supplied from the fuel supply valve 34 but heating of the fuel by the grow plug 36 is not performed. Note that there is another mode in which fuel is not supplied until the tip end portion 36 a of the glow plug 36 generates a certain amount of heat (a third operation mode). Note that, the fuel supply valve 34 and the glow plug 36 are normally maintained in a non-operating mode.

The engine 10 having the above configuration includes various sensors that electrically output signals indicating various kinds of detected values used for determination or estimation to the control unit 50. Here, some specific examples of the sensors will be described. An engine speed sensor 52 that detects an engine speed and an engine load sensor 54 that detects an engine load are provided. Note that a throttle opening sensor, an accelerator operation amount sensor, airflow meter, an intake pressure sensor, and the like may be used as the engine load sensor 54. Further, a flow sensor 56 that detects a flow rate of exhaust gas, namely, a flow velocity of the exhaust gas, in the exhaust passage 14 is provided. An airflow meter that is provided in an intake passage and detects an amount of intake air may be used as the flow sensor 56. Although not shown, an oxygen concentration senor that detects an oxygen concentration in the exhaust gas, a NOx sensor that detects an amount of NOx in the exhaust gas, and the like are also provided. Moreover, a first temperature sensor 58 that detects a temperature of the exhaust gas in the exhaust passage 14 is provided. Furthermore, a second temperature sensor 60 that detects a temperature of the third purification member 24 is provided.

The control unit 50 is formed of a microcomputer including a CPU, memory devices (ROM, RAM, etc.), an A/D converter, an input interface, an output interface, and the like. The various sensors described above are electrically connected to the input interface. Based on output signals or detection signals from the above various sensors, the control unit 50 electrically outputs operation signals or drive signals from the output interface such that the engine 10 is smoothly operated or activated according to a preset program and the like. Thus, the operation of the fuel injection valve, the operation of the fuel supply valve 34, the operation of the glow plug 36 (energization of the glow plug 36), the operation of the pump 40, and the like are controlled.

The control unit 50 has a function of controlling the entire engine 10 and a function as a control portion (control unit) in the temperature control device 30. That is, parts of the control unit 50 may function as a fuel supply control portion that controls the operation of the fuel supply valve 34 serving as the fuel supply portion, a heat generation control portion or a heating control portion that controls the operation of the glow plug 36 serving as the heating portion, and a pump control portion that controls the operation of the pump 40. An exhaust state detection device that detects a state of exhaust gas, namely, an exhaust state, in the exhaust passage 14 here includes an exhaust temperature detection device and an exhaust flow rate detection device. The exhaust temperature detection device includes the first temperature sensor 58 serving as an exhaust temperature detection portion and part of the control unit 50. The exhaust flow rate detection device includes the flow sensor 56 serving as an exhaust flow rate detection portion and part of the control unit 50.

In the engine 10, a fuel injection amount (a fuel amount) and a fuel injection timing are set such that a desired output is obtained, based on the amount of intake air, the engine speed, and the like, that is, the operation state of the engine represented by the engine load, the engine speed, and the like. Based on the fuel injection amount and the fuel injection timing, the fuel is injected from the fuel injection valve.

In the temperature control device 30, during an engine start-up, for example, the fuel supply valve 34 and the glow plug 36 are operated such that the temperatures of the exhaust gas purification members quickly increase to a predetermined temperature or higher, in particular, here, the temperature of the third purification member 24 quickly reaches a temperature within a predetermined activation temperature range. That is, the plug 36 is energized, and the fuel is injected from the fuel supply valve 34 toward the tip end portion 36 a of the glow plug 36. The gas containing such fuel or generated due to such fuel passes the oxidation promotion member 32 and its vicinity to reach the exhaust gas purification members. The supply of the gas to exhaust gas purification members during the engine start-up is started upon initiation of the engine star-up, and is continued until the temperature of the third purification member 24 becomes a predetermined temperature or higher within the predetermined activation temperature range of the third purification member 24. Note that the predetermined temperature within the predetermined activation temperature range of the third purification member 24 here is a lower limit temperature of the predetermined activation temperature range. For example, the predetermined temperature is set at 200° C. However, the supply of heating gas to the exhaust gas purification members during the engine start-up should be continued until an engine warm-up is completed, even if the temperatures of the exhaust gas purification members are quickly increased. In this case, whether the engine warm-up is completed or not is determined based on a temperature of engine coolant. For example, when the temperatures of the exhaust gas purification members are quickly increased and then the temperature of the coolant for the engine 10 becomes a predetermined temperature (e.g., 70° C.) or higher, the control unit 50 determines that the engine warm-up is completed. At this time, the control unit 50 stops the operations of the fuel supply valve 34 and the glow plug 36.

Further, after the temperature of the third purification member 24 reaches a temperature within the predetermined activation temperature range described above, the temperature control device 30 operates so as to maintain the temperature of the third purification member 24 within its predetermined activation temperature range. Specifically, when the temperature of the third purification member 24 is within a lower limit temperature range (e.g., within a range from 200° C. to 250° C.) that is a part of the predetermined activation temperature range, the fuel is supplied from the fuel supply valve 34 and the glow plug 36 is energized (the glow plug 36 is operated).

When the heating gas need to be supplied as described above, the fuel supply valve 34 and the glow plug 36 are operated. In addition, in order to more suitably heat the fuel supplied from the fuel supply valve 34, the operation of the glow plug 36 here is controlled, taking into account the state of the exhaust gas, namely, the exhaust state. Depending on the exhaust state in the exhaust passage 14, how the glow plug 36 cools may vary. This means that heat generation or heating operation of the glow plug 36 varies depending on the exhaust state. For example, exhaust gas with a lower temperature more easily cools the glow plug 36. Further, as the amount of intake air increases, that is, as the flow rate of the exhaust gas increases, the flow velocity of the exhaust gas flowing in the vicinity of the glow plug 36 increases and the glow plug 36 is more easily cooled by the exhaust gas. Therefore, the amount of electric power that is supplied to the glow plug 36 is controlled depending on the exhaust state, as will be described below.

With reference to a flowchart in FIG. 2, the control of the fuel supply from the fuel supply valve 34 and the control of the heating by the glow plug 36 will be described. Note that the routine shown by the flowchart in FIG. 2 is periodically executed.

The control unit 50 determines whether the exhaust gas purification members need to be heated (step S201). Cases in which the exhaust gas purification members need to be heated include a case in which the temperatures of the exhaust gas purification members are low or may become low during engine start-up as described above, and a case in which the particulate matter trapped by the second purification member 22 is removed. In such cases, it is determined that the exhaust gas purification members need to be heated (Yes in step S201).

When it is determined that the exhaust gas purification members need to be heated (Yes in step S201), outputs from the first temperature sensor 58 and the flow sensor 56 are obtained (step S203). This means that an exhaust gas temperature and an exhaust gas flow rate are detected.

Then, based on the obtained outputs, the amount of electric power that is supplied to the glow plug 36 (hereinafter, referred to as “electric power supply amount” where appropriate) is calculated (step S205). This means that the amount of electric power that is supplied to the glow plug 36 is calculated based on the exhaust gas temperature and the exhaust gas flow rate. Here, the electric power supply amount is calculated based on mapped data that is obtained, for example, empirically and set in advance. However, the electric power supply amount may be calculated based on an arithmetic expression that is obtained, for example, empirically and set in advance, or may be calculated based on both the mapped data and the arithmetic expression. The mapped data and the arithmetic expression are set such that a first correlation between the exhaust gas temperature and the electric power supply amount and a second correlation between the exhaust gas flow rate and the electric power supply amount are established. According to the first correlation, as the exhaust gas temperature decreases, the amount of electric power that is supplied to the glow plug 36 increases. According to the second correlation, as the exhaust gas flow rate increases, the amount of electric power that is supplied to the glow plug 36 increases. Note that, as described above, the amount of electric power that is supplied to the glow plug 36 is calculated based on the operation state of the engine, the temperatures of the exhaust gas purification members, and the like.

Based on the obtained electric power supply amount, the operation of the glow plug 36 is controlled (step S207). At this time, the fuel supply valve 34 is also operated (step S207). The amount of fuel that is supplied from the fuel supply valve 34 is set constant here, although it may be variable. For example, the amount of fuel that is supplied from the fuel supply valve 34 may be varied based on the temperatures of the exhaust gas purification members. Note that with the operation control for the fuel supply valve 34 and the glow plug 36 in step S207, the fuel supply valve 34 and the glow plug 36 may be placed in the first operation mode or the second operation mode described above.

On the other hand, when it is determined that the exhaust gas purification members need not be heated (No in step S201), the operations of both the fuel supply valve 34 and the glow plug 36 are stopped (step S209), that is, the fuel supply valve 34 and the glow plug 36 are placed in a non-operating mode.

As described above, when the fuel is supplied from the fuel supply valve 34, the amount of electric power that is supplied to the glow plug 36 is controlled so as to be variable based on the exhaust state, especially the exhaust gas temperature and the exhaust gas flow rate. Therefore, regardless of the exhaust state, the supplied fuel can be appropriately heated or combusted. Moreover, since the amount of electric power that is supplied to the glow plug 36 is controlled as described above, it is possible to reduce the total amount of electric power that is supplied to the glow plug 36. Consequently, power consumption is decreased, thereby improving fuel efficiency.

Next, a second embodiment of the invention will be described. An exhaust gas control apparatus 101 according to the second embodiment is applied to an engine, as in the case of the exhaust gas control apparatus 1 according to the first embodiment described above. However, the exhaust gas control apparatus 101 according to the second embodiment is different from the exhaust gas control apparatus 1 according to the first embodiment in terms of operation control of the fuel supply valve 34 and the glow plug 36. Hereinafter, the differences will be mainly explained. Note that the configuration of the exhaust gas control apparatus 101 according to the second embodiment is generally the same as that of the exhaust gas control apparatus 1 according to the first embodiment. Therefore, structural elements corresponding to those described in the first embodiment are denoted by the same reference numerals as in the first embodiment, and description of such structural elements is omitted.

Hereinafter, control in the second embodiment will be described. The amount of electric power that is supplied to the glow plug 36 is controlled based on the exhaust state and the amount of fuel that is supplied from the fuel supply valve 34. This is because the fuel supplied from the fuel supply valve 34 may cool the glow plug 36, and the amount of heat generated by the glow plug 36 or heating effect produced by the glow plug 36 may vary depending on the amount of supplied fuel.

First, the control unit 50 determines whether the exhaust gas purification members need to be heated (step S301) in the same manner as in step S201 described above. When it is determined that the exhaust gas purification members need to be heated (Yes in step S301), outputs from the first temperature sensor 58 and the flow sensor 56 are obtained (step S303) in the same manner as in step S203. Then, based on these outputs, a reference electric power amount for the glow plug 36 is calculated (step S305). The calculation of the reference electric power amount corresponds to the calculation of the electric power supply amount in step S205.

Further, the control unit 50 calculates the amount of fuel that is supplied from the fuel supply valve 34 (hereinafter, referred to as “fuel supply amount” where appropriate) (step S307). This calculation is performed based on the result of determination as to whether the exhaust gas purification members need to be heated in step S301, data obtained, for example, empirically and set in advance, and so on. Specifically, in order to increase the temperature of the third purification member 24 to the predetermined temperature described above, the fuel supply amount required for such temperature increase is calculated. In order to remove particulate matter from the second purification member 22, the fuel supply amount required for such removal is calculated. Note that, in step S307, the fuel supply amount may be calculated more precisely, based on the operation state of the engine, the temperatures of the exhaust gas purification members and/or the exhaust state, etc.

A part of the control unit 50, which functions as a correction coefficient calculation portion, calculates a correction coefficient (step S309). This correction coefficient is calculated based on the output from the first temperature sensor 58 obtained in step S303 and the fuel supply amount calculated in step S307. This means that the correction coefficient is calculated based on the exhaust gas temperature and the fuel supply amount. Here, the correction coefficient is calculated based on mapped data that is obtained, for example, empirically and set in advance. However, the correction coefficient may be calculated based on an arithmetic expression that is obtained, for example, empirically and set in advance, or may be calculated based on both the mapped data and the arithmetic expression. The mapped data and the arithmetic expression are set such that a third correlation between the exhaust gas temperature and the electric power supply amount and a fourth correlation between the fuel supply amount and the electric power supply amount are established. According to the third correlation, as the exhaust gas temperature decreases, the amount of electric power that is supplied to the glow plug 36 increases. According to the fourth correlation, as the fuel supply amount increases, the amount of electric power that is supplied to the glow plug 36 increases. Note that the correction coefficient may be calculated based on only the fuel supply amount calculated in step S307.

Then, based on the reference electric power amount calculated in step S305 and the correction coefficient calculated in step S309, the amount of electric power that is supplied to the glow plug 36 (hereinafter, referred to as “electric power supply amount” where appropriate) is calculated (step S311). Here, the amount of electric power that is supplied to the glow plug 36 is calculated by multiplying the reference electric power amount by the correction coefficient.

As a result, based on the fuel supply amount calculated in step S307 and the electric power supply amount calculated in step S311, the operations of the fuel supply valve 34 and the glow plug 36 are controlled (step S313). Note that with the operation control for the fuel supply valve 34 and the glow plug 36 in step S313, the fuel supply valve 34 and the glow plug 36 may be placed in the above-described first operation mode or second operation mode.

On the other hand, when it is determined that the exhaust gas purification members need not be heated (No in step S301), the operations of both the fuel supply valve 34 and the glow plug 36 are stopped (step S315).

The invention has been described based on the above two embodiments. However, the invention is not limited to the above embodiments, and may be implemented in other embodiments. For example, the sensors are used to detect the exhaust gas temperature and the exhaust gas flow rate in the above embodiments. However, the exhaust gas temperature and the exhaust gas flow rate may be calculated, that is, estimated, based on the operation state of the engine or the like. In addition, the temperatures of the exhaust gas purification members may also be calculated, that is, estimated, based on the operation state of the engine or the like.

In the above embodiments, the fuel supply valve is used as the fuel supply portion, and the fuel that is the same as that used in the engine is supplied from the fuel supply valve. However, other fuels may be used, and for example, alcohols such as ethanol, and methanol may be used as an additive.

Moreover, the number, type, configuration, and arrangement order of the exhaust gas purification members provided in the exhaust passage are not limited to those in the above embodiments. The number of exhaust gas purification members may be one, two, or four or more. For example, another exhaust gas purification member including an oxidation catalyst may be provided downstream of the third purification member described above. As the exhaust gas purification member, various catalysts, filters, and the like may be used. In addition, the oxidation promotion member described above need not include the oxidation catalyst having the configuration described above. The oxidation catalyst may include some other catalyst having an

Oxidation function. Note that the oxidation promotion member need not be provided.

Furthermore, the invention is applied to a diesel engine in the above embodiments. However, the invention is not limited to this. The invention is applicable to various types of engines such as a port-injection gasoline engine and an in-cylinder injection gasoline engine. Further, the fuel that is used is not limited to light oil or gasoline, and alcohol fuel, liquefied natural gas (LNG), and the like may be used. In addition, the invention may be applied to an engine with any number of cylinders, any cylinder arrangement, or the like.

The exhaust gas control apparatus according to the invention is applicable to technologies other than engine technology. For example, the exhaust gas control apparatus according to the invention may be used in plant facilities.

It is to be understood that the invention is intended to cover various modifications and equivalent arrangements within the sprit and scope of the invention described in claims. That is, the invention is intended to cover various modifications, applications and equivalents within the spirit of the invention defined by claims. 

1. An exhaust gas control apparatus, comprising: an exhaust gas purification member that is provided in an exhaust passage; a fuel supply portion that is provided so as to supply fuel to a portion of the exhaust passage, which is upstream of the exhaust gas purification member; a heating portion that is disposed between the fuel supply portion and the exhaust gas purification member; and a control portion that controls an amount of electric power that is supplied to the heating portion, based on an exhaust gas temperature and an exhaust gas flow rate.
 2. The exhaust gas control apparatus according to claim 1, wherein the control portion increases the amount of electric power that is supplied to the heating portion as the exhaust gas temperature decreases.
 3. The exhaust gas control apparatus according to claim 1, wherein the control portion increases the amount of electric power that is supplied to the heating portion as the exhaust gas flow rate increases.
 4. The exhaust gas control apparatus according to claim 1, wherein the control portion executes a control of correcting the amount of electric power that is supplied to the heating portion, based on an amount of fuel that is supplied from the fuel supply portion.
 5. The exhaust gas control apparatus according to claim 4, wherein the control portion executes the control of correcting the amount of electric power that is supplied to the heating portion, such that the amount of electric power that is supplied to the heating portion increases as the amount of fuel that is supplied from the fuel supply portion increases.
 6. An internal combustion engine comprising the exhaust gas control apparatus according to claim
 1. 7. A method for controlling an exhaust gas control apparatus which includes an exhaust gas purification member that is provided in an exhaust passage, a fuel supply portion that is provided so as to supply fuel to a portion of the exhaust passage, which is upstream of the exhaust gas purification member, and a heating portion that is disposed between the fuel supply portion and the exhaust gas purification member, the method comprising: detecting an exhaust gas temperature; detecting an exhaust gas flow rate; and controlling an amount of electric power that is supplied to the heating portion, based on the exhaust gas temperature and the exhaust gas flow rate. 